Fluoropolymers include, for example, crosslinked fluoroelastomers, curable fluoroelastomer gums, and semi-crystalline fluoroplastics. Fluoroelastomers generally are tolerant to high temperatures and harsh chemical environments. Thus, they are particularly useful as seals, gaskets, and molded parts in systems that are exposed to elevated temperatures and/or corrosive chemicals. Such parts are used in the automotive, chemical processing, semiconductor, aerospace, and petroleum industries, among others.
Fluoroelastomers often include a cure-site component to facilitate cure in the presence of a catalyst. One class of useful cure-site components includes nitrile group-containing monomers, for which organotin catalysts have been used as curing components. Such curatives can leave undesirable extractable metal residues in the cured product and are undesirable for environmental reasons. Ammonia-generating compounds have also been used as a cure system component. These cure systems lack the desired level of rheology control during processing. In addition, most known fluoroelastomers are cured into colored or opaque materials. Perfluoroelastomers described as colorless and/or transparent are known, but the compression set of these compositions is rather high even when measured at relatively low temperatures (up to 200° C.).